This invention relates to a water-cooled, four-cycle combustion engine for outboard motors and more particularly to an improved cooling and lubricating system for such an engine.
As is well known, many outboard motors have their engines cooled by liquid from the body of water in which they operate. This water is circulated through the cylinder block and cylinder head of the engine to cool the engine. In addition, the exhaust gases are discharged downwardly through the driveshaft housing for expulsion through the lower unit. It is desirable to provide cooling for the exhaust gases before they are discharged into the lower unit so as to avoid unnecessary overheating of the driveshaft housing and lower unit. With a two-cycle engine, this is relatively easily accomplished since the exhaust gases are discharged from the cylinder block or crankcase and the engine cooling outlet is positioned in proximity to this. Thus, it is possible to provide a cooling jacket around the exhaust port of a two-cycle engine to cool the exhaust gases before discharge into the driveshaft housing and lower unit. With a four-cycle engine, however, the exhaust gases are discharged from the cylinder head and cooling of them with conventional four-cycle engines is difficult. One method which has been proposed for cooling the exhaust gases of a four-cycle outboard motor engine is to surround the exhaust manifold with a cooling jacket. This presents difficulties in that piping is required to deliver the coolant to this cooling jacket and return it to the body of water in which the motor is operated. Obviously, this also increases the cost of the engine. Another alternative is to discharge the coolant into the exhaust manifold to cool the exhaust cases. Again, plumbing is required for this. In addition, such an arrangement gives rise to the possibility that the coollant may leak back into the combustion chambers and cause severe damage to the internal components of the engine.
It is, therefore, a principal object of this invention to provide a cooling arrangement for a four-cycle water-cooled engine that permits cooling of the exhaust gases at their point of discharge.
It is another object of the invention to provide an improved liquid cooling arrangement for a four-cycle internal combustion engine that permits cooling of the exhaust gases.
It is a further object of this invention to provide a cooling jacket for the exhaust system of an internal combustion engine of the water-cooled type.
It is yet a further object of this invention to provide an improved cylinder head construction for a water-cooled four-cycle engine that permits the cooling jacket of the engine to cool the exhaust gases as they are discharged from the cylinder head.
For obvious reasons, the internal combustion engine of an outboard motor must be extremely compact. This requirement for compactness has limited the use of four-cycle engines for such applications. Because of the greater complexity of such engines, it has been difficult with conventional engines to make them compact enough to permit use as an outboard motor power plant.
It is, therefore, a further object of this invention to provide an improved cooling system for an outboard motor that permits a compact construction.
In connection with water-cooled outboard motors, a thermostat is employed so as to insure that the engine is maintained at a desirable operating temperature. If the engine is, however, of the four-cycle type, it is difficult to maintain compactness particularly for the mounting of the thermostat.
It is, therefore, a still further object of this invention to provide a thermostat location for water-cooled, four-cycle internal combustion engines in which the thermostat location is in what would be otherwise dead space of the engine.
As has been noted, the coolant for a water-cooled outboard motor is drawn from the body of water in which the motor operates. Frequently, the motors are operated in salt water which, as is well known, is extremely corrosive. This is particularly true when the castings of the engine in which the cooling jacket is formed are formed from lightweight materials or different materials that give rise to electrogalvanic action. The corrosion of the engine components can be avoided even when operating in marine environments if a sacrificial anode is placed in the engine cooling system. Again, however, the compact arrangement of the engine for an outboard motor makes it difficult to position and employ such a sacrificial anode.
It is, therefore, a still further object of this invention to provide an improved mounting arrangement for a sacrificial anode in the cooling system of an internal combustion engine.
It is another object of the invention to provide a method for mounting a sacrificial anode in an internal combustion engine wherein the anode is mounted in an opening that is provided in a wall of the engine which normally must be closed in another manner and which is used to position a mold or core during casting of the engine.
It is the normal practice with internal combustion engines for use as outboard motors to position the engine so that the crankshaft rotates about a vertically extending axis. When the engine is of the four-cycle type embodying a camshaft, this generally means that the camshaft also rotates about a vertically extending axis. With such orientations, it is difficult to insure adequate lubrication of all of the wearing components of the camshaft. Specifically, the vertical orientation of the camshaft makes it difficult to insure adequate lubrication of the cam lobes and the follower elements be they rocker arms or tappets.
It is, therefore, a still further object of this invention to provide an improved lubricating system for an engine having its camshaft rotating about a vertically extending axis.
It is a yet further object of this invention to provide an improved lubricating system for the camshaft of an internal combustion engine.